Hey! Just wanted to share what worked for my install because it took me a while to figure out and I'd love to save others some time.
My specs:
Motherboard: ASRock H61M-VS (ethernet: Atheros AR8151, audio: VIA VT1705)
Processor: Intel i5-2300 (Sandy Bridge)
Graphics: NVIDIA GTX 970
Everything went smoothly with my previous Yosemite install because I had a different (more compatible) graphics card. Updating to El Capitan with the 970 was tricky though....
[Success] El Capitan on ASRock H61M-VS, Sandy Bridge i5, GTX 970
My specs:
Motherboard: ASRock H61M-VS (ethernet: Atheros AR8151, audio: VIA VT1705)
Processor: Intel i5-2300 (Sandy Bridge)
Graphics: NVIDIA GTX 970
Everything went smoothly with my previous Yosemite install because I had a different (more compatible) graphics card. Updating to El Capitan with the 970 was tricky though....
[Success] El Capitan on ASRock H61M-VS, Sandy Bridge i5, GTX 970